Janus fluid with fixed patch orientations: theory and simulations

TL;DR

This paper combines analytical modeling and simulations to investigate the thermophysical properties of a Janus fluid with fixed patch orientations, revealing accurate structural and thermodynamic insights despite approximations.

Contribution

It introduces a novel analytical approach mapping the Janus fluid onto a binary mixture with asymmetric interactions, extending the sticky limit approximation for precise property estimation.

Findings

Analytical theory closely matches simulation results.

The model accurately predicts structural and thermodynamic properties.

The approach simplifies complex anisotropic interactions into a quasi-isotropic framework.

Abstract

We study thermophysical properties of a Janus fluid with constrained orientations, using analytical techniques and numerical simulations. The Janus character is modeled by means of a Kern-Frenkel potential where each sphere has one hemisphere of square-well and the other of hard-sphere character. The orientational constraint is enforced by assuming that each hemisphere can only point either North or South with equal probability. The analytical approach hinges on a mapping of the above Janus fluid onto a binary mixture interacting via a "quasi" isotropic potential. The anisotropic nature of the original Kern-Frenkel potential is reflected by the asymmetry in the interactions occurring between the unlike components of the mixture. A rational-function approximation extending the corresponding symmetric case is obtained in the sticky limit, where the square-well becomes infinitely narrow and deep, and allows a fully analytical approach. Notwithstanding the rather drastic approximations in the analytical theory, this is shown to provide a rather precise estimate of the structural and thermodynamical properties of the original Janus fluid.